1. Field of the Invention
This invention relates to a process for improving the palatability of dry pet food. More particularly, this invention relates to a process for enhancing the flavor of dry pet food which has been stored so that the acceptance thereof by cats is increased.
It should be understood that the expression "dry pet food," as used herein, includes such foods having a low moisture content as distinguished from pet foods having intermediate or relatively high moisture contents. Pet foods having intermediate moisture levels generally contain from about 20 to 40 percent moisture. For bacteriostatic purposes, such pet foods are formulated to contain relatively high levels of water soluble solids, e.g., sugars, polyglycol alcohols, salt, etc. in order to bind the free water present and also a low pH level is provided in the pet food. Dry pet foods, on the other hand, are formulated to contain less than about 15 percent moisture and the free water content is generally insufficient to support the growth of contaminating microorganisms.
Dry pet foods exhibit a number of advantages over pet foods having higher moisture contents. The dry foods are generally more nutritious on an equal weight basis, require less expensive packaging, have better keeping qualities and are more convenient to use.
Domestic animals, particularly cats, are notoriously fickle in their food preferences. As a result, their owners frequently change types and brands of cat food in order to maintain their pets in a healthy and contented condition. For the most part, the only way to determine the gastronomic preferences of cats is by trial and error.
2. Description of the Prior Art
There are a number of processes disclosed in the art for improving the palatability and other characteristics of dry pet food. U.S. Pat. No. 3,115,409 to Hallinan et al. is directed to pet foods having a high acid content and a minimum disclosed moisture content of 30 percent. The pH of the pet food is adjusted to low levels and then the pet food is cooked to alter the proteinaceous material contained therein. This type of procedure is commonly practiced in the food industry to inhibit bacterial decomposition and to hydrolyze proteinaceous materials in order to develop more flavorful products. In order for the reaction to take place, relatively large quantities of water are necessary. U.S. Pat. No. 3,139,342 to Linskey relates to an animal food process wherein the food is produced in the form of pellets which may be coated with various taste enhancing and/or nutrition supplementing materials, e.g., fat and Vitamin A. U.S. Pat. No. 3,203,806 to Young relates to a pet food having acetamide and acetic acid incorporated therein for improved palatability. The palatability improvers may be added to dry or semi-dry pet foods by being sprayed thereon. U.S. Pat. No. 3,539,357 to Appleman et al. relates to a method of preparing animal food having a relatively high moisture content whereby heated meat tissue is treated with an acid to produce a breakdown of the proteins and comminuting the treated material. U.S. Pat. No. 3,615,647 to Kassens is directed to a porous, expanded animal food in the form of chunks coated with fat which coating is, in turn, overlaid with a coating of dextrin. U.S. Pat. No. 3,679,492 to Mohrman et al. relates to a method for improving the palatability of dry cat food by coating particles of the food with fat and a flavor enhancing acid, specifically, citric, phosphoric or hexamic acids. U.S. Pat. No. 3,708,306 to Appleman relates to a pet food containing psyllium byproducts wherein dicalcium phosphate is incorporated. The dicalcium phosphate is blended into the pet food together with other ingredients in the form of a batter which is then baked. U.S. Pat. No. 3,930,031 to Kealy is directed to a cat food composition having a coating comprising a flavor enhancing mixture of phosphoric and citric acids.
In general, cats seem to exhibit a preference for foods having an acidic reaction. The degree of acceptance of a food is apparently determined largely through the cats' highly developed sense of smell. Materials applied to the surface of dry pet food affect its acceptance by cats to a greater degree than do the same materials incorporated into the body of the food. Presumably, this is due to the fact that the cats' olfactory organs can more readily detect the smell of these materials when such are on the surface of the food.
The application of certain acids to the surface of dry cat food, while apparently having a positive effect on palatability, is not entirely satisfactory. Such acids present handling problems and, since they are corrosive, expensive equipment must be used in processes employing the same. Moreover, since the acids are applied in liquid form, they may diffuse into the body of the food upon storage, thus reducing their effect on palatability and acceptance.